Bump sphinx-notfound-page from 0.8 to 0.8.3

Bumps [sphinx-notfound-page](https://github.com/readthedocs/sphinx-notfound-page) from 0.8 to 0.8.3.
- [Release notes](https://github.com/readthedocs/sphinx-notfound-page/releases)
- [Changelog](https://github.com/readthedocs/sphinx-notfound-page/blob/main/CHANGELOG.rst)
- [Commits](readthedocs/sphinx-notfound-page@0.8...0.8.3)

---
updated-dependencies:
- dependency-name: sphinx-notfound-page
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements_docs.txt

@@ -10,7 +10,7 @@ QtPy==2.1.0
 Sphinx==5.0.2
 sphinx-autobuild==2021.3.14
 sphinx-copybutton==0.5.0
-sphinx-notfound-page==0.8
+sphinx-notfound-page==0.8.3
 sphinx-rtd-theme==1.0.0
 sphinxcontrib-napoleon==0.7
 sphinxcontrib-websupport==1.2.4